UNIVERSITY   OF   CALIFORNIA 

fa. 

COLLEGE    OF    AGRICULTURE 


STAT'°N 


FEB  9    1934        CIRCULAR  NO.  m 

Revised  June,  1921 

F?  A  p  y 

THE  USE  OF  LIME  AND  GYPSUM 
ON  CALIFORNIA  SOILS 

BY  J.  W.  NELSON 


Much  confusion  exists  in  many  minds  with  reference  to  the  actual 
nature  of  lime  and  its  use.  The  following  brief  statements  are  in- 
tended to  clear  up  this  confusion  and  to  answer  frequently  recurring 
questions  on  the  important  subjects  of  lime  and  gypsum  and  their  uses. 

THE   NATURE   AND   FUNCTIONS    OF   LIME 

The  term  ' '  lime, "  as  we  may  employ  it  in  the  Agricultural  sense, 
includes  the  following  materials:  (1)  Burnt  lime  or  quicklime  (oxide 
of  calcium),  (2)  hydrated  or  water-slaked  lime  (hydrate  of  calcium), 
and  (3)  ground  limestone  (carbonate  of  calcium).  In  addition  a  form 
of  lime  known  as  air-slaked  lime  is  available,  which  may  approach  in 
chemical  composition  the  ground  limestone.  Air-slaked  lime  results 
from  the  action  of  carbonic  acid  gas  on  water-slaked  lime  or  from  that 
of  water  and  carbonic  acid  gas  on  burnt  lime  or  quicklime.  Either 
burnt  lime,  or  hydrated  or  water-slaked  lime,  will  change  to  air-slaked 
lime  if  allowed  to  lie  in  the  open  air  long  enough.  The  action  is  rather 
slow  in  the  center  of  the  pile,  however,  and  thus  it  happens  that  so- 
called  air-slaked  lime  frequently  consists  of  a  considerable  proportion 
of  quicklime,  or  of  water-slaked  lime,  as  the  case  may  be,  and  is  there- 
fore not  so  fully  carbonated  as  one  would  expect.  The  total  amount 
of  air-slaked  lime  of  the  variety  just  described  that  is  available  on  the 
market  is  very  small.  There  is  a  form  of  air-slaked  lime,  however,  that 
is  available  at  present  in  considerable  quantities.  This  form  is  a  by- 
product of  sugar  refining,  and  in  chemical  composition  is  much  more 
like  ground  limestone  than  the  ordinary  forms  of  air-slaked  lime  just 
discussed.  This  so-called  "sugar  house"  refuse  lime  contains,  in  the 
dry  state,  from  70  to  80  per  cent  of  calcium  carbonate.  It  is  usually 
in  a  very  fine  state  of  division  and  for  that  reason  is  superior  to  ground 
limestone,  even  though  the  latter  may  contain  a  larger  proportion  of 
actual  calcium  carbonate. 


University  of  California 

Southern  Regional 

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»  Even  in  the  agricultural  sense,  the  term,  lime  does  not  include 
gypsum.  The  latter  is  an  entirely  different'  Substance  from  the  three 
named  above,  as  will  be  explained  later.  Speaking  with  the  exactness 
of  the  chemist,  the  term  "lime"  is  applied  only  to  burnt  lime  (quick- 
lime) or  calcium  oxide.  Just  how  the  three  materials  discussed  from 
the  agricultural  point  of  view  under  the  name  lime  are  to  be  employed, 
and  where  one  is  to  be  preferred  to  the  other,  if  at  all,  are  questions 
which  are  answered  below. 

Before  going  into  a  detailed  discussion  of  the  mission  or  function 
of  lime  in  soils,  it  is  well  to  state  clearly  the  relative  values  in  practice 
of  the  three  different  kinds  of  lime,  (1)  the  burnt,  caustic,  or  quick- 
lime; (2)  the  hydrated  or  water-slaked  lime,  and  (3)  the  carbonate 
or  the  air-slaked  lime.  The  value  of  these  materials  depends  largely 
upon  the  amount  of  calcium  oxide  which  they  contain.  Quicklime  is 
nearly  all  calcium  oxide.  Hydrated  or  water-slaked  lime  contains  less 
calcium  oxide  than  quicklime,  in  about  the  proportion  of  10  to  13. 
It  takes  2643  pounds  of  hydrated  lime  to  carry  a  quantity  of  calcium 
oxide  equivalent  to  that  carried  by  2000  pounds  of  quicklime  when 
both  materials  ar«r  pure.  Nevertheless,  for  practical  purposes,  they 
are  not  to  be  considered  as  very  different,  since  they  are  rarely  pure. 
Water-slaked  lime,  however,  possesses  advantages  over  ground  lime- 
stone and  quicklime  in  fineness  of  division  and  in  purity.  Thoroughly 
air-slaked  lime,  like  sugar-house  refuse  lime  and  ground  limestone, 
contains  only  a  little  more  than  half  the  amount  of  calcium  oxide  that 
the  quicklime  does  and  therefore  about  twice  as  much  of  either  should 
be  employed  if  it  is  to  be  used  in  place  of  burnt  lime.  If  the  ground 
limestone  is  not  very  pure,  that  is,  if  it  contains  less  than  98  per  cent 
of  calcium  carbonate,  proportionately  more  should  be  used,  according 
to  its  composition,  than  would  be  required  if  burnt  lime  were  used. 
The  same  is  true  of  sugar-house  refuse  lime.  As  the  water-slaked  lime 
has  an  advantage  over  the  burnt  lime,  owing  to  its  fineness  of  division, 
so,  for  the  same  reason,  the  sugar-house  refuse  lime  has  an  advantage 
over  the  ground  limestone.  It  must  be  remembered,  however,  in  all 
these  cases,  that  the  total  amount  of  calcium  oxide  obtained  should  be 
the  first  consideration  when  purchasing  any  of  these  materials.  Other 
rules  for  making  a  choice  depend  upon  conditions  which  are  discussed 
below.  Relative  money  values  can  be  determined  at  any  time  with 
the  help  of  the  foregoing  explanation  of  the  comparative  relations 
existing  between  the  different  lime  materials.  In  this  connection,  the 
cost  of  handling  larger  quantities,  and  the  additional  freight  rates 
involved,  should  always  be  taken  into  consideration  in  calculating 
the  actual  and  relative  cost  of  the  different  materials.  The  prices  for 


lime  vary  in  this  state,  to  the  knowledge  of  the  writer,  from  $2  per  ton 
up  to  $15  per  ton,  and  there  seems  to  be  no  uniformity  of  price  based 
on  actual  lime  content  or  on  fineness  of  division.  Local  circumstances 
of  various  kinds  usually  set  the  prices.  Ground  limestone  and  sugar- 
house  refuse  lime  have  been  selling  at  rates  varying  from  $3.50  to 
$6.50  per  ton,  and,  in  most  cases,  very  little  of  the  other  forms  of  lime 
is  available  on  the  market  for  agricultural  uses.  A  list  of  some  of  the 
principal  firms  which  sell  lime  in  different  forms  may  be  obtained  by 
addressing  the  College  of  Agriculture,  Berkeley,  California. 
Let  us  now  consider  the  function  of  lime  materials  in  soils. 

1.  Lime  materials  have  the  power  of  improving  the  crum-structure 
of  clay  and  making  it  more  pervious  to  water  and  air.    Therefore  lime 
makes  clays  and  clay  adobe  soils  looser,  tends  to  prevent  packing  and 
baking,  makes  plowing  and  cultivating  easier,  and,  in  general,  makes 
the  soil  physically  a  healthful  medium  for  plant  growth. 

2.  Lime  materials  tend  to  make  "sour"  soils  "sweet."     Speaking 
more  correctly,  they  tend  to  change  an  acid  soil  condition  to  a  less 
acid  one.    Acidity  of  soils  is  detrimental  to  the  best  growth  of  many 
agricultural  crops. 

3.  Lime  materials  are  necessary  for  the  growth  of  beneficial  bac- 
teria and  other  micro-organisms  of  the  soil.  Lime  furnishes  the  element 
calcium,  which  is  as  essential  to  them  as  to  the  higher  plants.     It 
promotes  a  slightly  alkaline  condition,  which  is  probably  ideal  for  their 
development.    By  its  physical  effect,  lime  produces  favorable  air  and 
moisture  conditions  for  bacteria,  as  described  above. 

.  4.  Lime  materials  promote  the  normal  decay  of  organic  matter  in 
the  soil  through  their  effects  on  the  agencies  of  decay  described  above. 
The  normal  decay  of  organic  matter  in  soil  prevents  the  accumulation 
of  certain  poisonous  materials  that  are  detrimental  to  plant  growth. 

5.  Lime  will  not  neutralize  the  toxic  effects  of  sodium  carbonate 
or  black  alkali. 

THE  NATURE  AND  FUNCTION  OF  GYPSUM 

Gypsum  is  the  sulfate  of  calcium  and  therefore  is  not  the  same  as 
' '  lime, ' '  nor  the  same  as  any  of  the  three  forms  of  the  latter  that  have 
been  described.  The  only  thing  which  gypsum  has  in  common  with 
the  three  lime  materials  named,  as  regards  chemical  composition,  is 
that  it  contains  the  element  of  calcium.  Its  functions  in  soils  may 
be  briefly  stated  as  follows : 

1.  Gypsum  exerts  a  physical  effect  similar  to  that  of  lime  on  the 
clay  and  adobe  soils  (see  above). 


2.  Gypsum,  like  lime,  serves  as  a  source  of  the  element  calcium  (see 
above). 

3.  Gypsum,  like  lime,  stimulates  the  beneficial  soil  organisms  in 
the  nodules  on  roots  of  leguminous  plants,  like  the  peas,  beans,  vetches, 
alfalfas,  and  clovers. 

4.  Gypsum  does  not  make  "sour"  soil  "sweet."     It  ivill   not 
change  an  acid  into  a  slightly  alkaline  sail  as  do  the  lime  materials. 
Gypsum  possesses  no  alkalinity,  and  therefore  will  not  be  of  assistance 
in  cases  of,  or  act  as  a  corrective  to,  "sourness"  or  acidity  in  soils. 

5.  Gypsum  will  neutralize  the  toxic  effects  of  sodium  carbonate  or 
" black  alkali." 

LIME   VERSUS    GYPSUM 

The  question  is  frequently  asked  whether  or  not  "lime  or  gyp- 
sum" will  correct  a  certain  difficulty  in  soils.  This  confusion  of 
two  distinct  types  of  substances  has  done  much  harm,  and  the  reader 
is  asked  to  note  carefully  the  statements  made  above  with  respect 
to  each  in  order  that  errors  may  be  avoided.  As  already  stated, 
there  is  at  least  one  very  important  function  that  lime  performs  in 
the  soil  which  gypsum  cannot  perform.  If  soils  need  correction  for 
acidity,  the  lime  materials  will  serve  but  not  gypsum.  Too  much 
emphasis  cannot  be  placed  on  this  distinction.  In  fact,  to  be  on  the 
safe  side,  the  use  of  lime  is  advised  in  all  cases  where  there  is  any 
doubt,  except  for  neutralizing  black  alkali.  The  distinct  and  limited 
uses  for  gypsum  are  described  below,  however,  to  serve  as  a  guide. 

NEED   FOR   LIME    IN   CALIFORNIA 

-  , — "-"  >srr-s 

Generally  speaking,  it  is  likely  that  those  areas  in  California  re- 
ceiving more  than  twenty  inches  of  rainfall,  such  as  the  northern  coast 
counties,  much  of  the  Sacramento  Valley  and  the  Sierra  Nevada  and 
Coast  Range  mountains,  have  lost  their  lime  from  the  upper  few  feet 
of  soil.  Other  old  upland  soil  deposits,  such  as  the  red  hardpan  lands 
of  the  Sacramento  and  San  Joaquin  valleys  and  the  old  marine^  ter- 
races and  valley  slopes  in  Santa  Cruz  and  Monterey  counties  and 
southward  along  the  coast  to  Mexico,  are  usually  either  in  an  acid  or 
neutral  condition.  Lands  subject  to  overflow,  those  occupying  stream 
bottoms  or  recently  formed  valley  slopes  with  less  than  twenty  inches 
of  rainfall,  usually  have  lime  well  distributed  through  the  soil  mass 
and  are  less  likely  to  need  this  constituent.  All  soils,  however,  receiv- 
ing large  applications  of  organic  matter  should  be  examined  period- 
ically for  their  lime  requirements. 


LIME   ON    HEAVY    SOILS 

No  determination  needs  to  be  made  to  inform  the  owner  of  heavy 
land  whether  or  not  lime  is  necessary  to  improve  the  soil's  structure 
in  the  ways  described  above.  The  decision  both  as  to  the  amount  to 
apply  and  as  to  the  feasibility  of  applying  it  must  be  made  on  the 
basis  of  the  cost  of  lime  and  the  degree  of  "running  together"  or 
baking  which  is  characteristic  of  the  soil.  From  one  to  two  tons  of 
burnt  lime  or  of  hydrated  lime,  or  from  two  to  four  tons  of  ground 
limestone,  may  be  safely  applied  to  improve  the  working  qualities  of 
heavy  soils.  Application  may  be  made  by  means  of  one  of  the  several 
types  of  lime-spreading  machines  or  the  lime  may  be  deposited  in  piles 
and  spread  with  a  shovel.  It  should  be  harrowed  in  and  if  possible 
followed  by  sufficient  moisture  to  distribute  it  through  the  soil  mass 
one  or  more  feet  in  depth. 

Burnt  lime  and  hydrated  lime  are  to  be  preferred  to  carbonate 
of  lime  for  improving  heavy  soils  if  the  cost  will  allow.  The  first  two 
forms  act  more  vigorously  and  more  quickly.  Applications  of  lime 
are  best  made  after  fall  or  winter  plowing  or  one  or  more  months  prior 
to  planting.  This  is  particularly  important  if  either  burnt  lime  or 
hydrated  lime  is  employed. 

LIME  ON   "SOUR"   OR  ACID  SOILS 

... 

If  "sour"  soils  are  also  heavy  clays  or  clay  adobes,  the  recom- 
mendations made  above  for  the  use  of  lime  on  heavy  soils  should  be 
followed.  If  they  are  loams,  silts,  or  sands,  ground  limestone  is 
usually  to  be  preferred  to  the  other  forms  of  lime. 

On  some  of  the  acid  soils  in  the  northwest  coast  counties  and  in 
other  localities  in  the  state,  the  use  of  lime  alone  has  apparently  been 
of  little  or  no  benefit  to  alfalfa,  but  lime  added  with  about  two  hundred 
pounds  of  sulfur  per  acre  has  given  from  one  hundred  to  three  hun- 
dred per  cent  increase  in  yields  of  alfalfa  through  a  two-year  period. 
Sulfur  alone  in  the  test  above  mentioned  gave  an  increase  of  about 
thirty-five  per  cent  for  alfalfa. 

To  test  the  soil  for  sourness  or  acidity,  one  may  proceed  as  follows : 
Mix  some  of  the  surface  soil  to  be  tested  and  moisten  thoroughly. 
Mold  it  into  a  ball  of  wet  earth  about  three  or  four  inches  in  diameter, 
care  being  taken  that  perspiration  from  the  hands  does  not  come  in 
contact  with  the  soil.  Break  the  ball  in  two  and  on  one  of  the 
broken  surfaces  place  two  strips  of  red  litmus  paper  previously" 
moistened  with  clean  boiled  water.  (Litmus  paper,  both  red  and 
blue,  may  be  obtained  in  drug  stores.)  If  possible,  do  not  touch  the 


moistened  litmus  paper  with  the  fingers.  Set  the  broken  surfaces  of 
earth  together  again  and  press  tightly.  Perform  the  same  test  with 
another  ball  of  earth,  but  use  blue  instead  of  red  litmus  paper.  Allow 
the  balls  of  earth  to  lie  undisturbed  for  half  an  hour ;  then  open,  and 
if  the  red  litmus  paper  has  turned  blue  no  lime  is  needed.  If  it 
remains  red,  and  the  blue  litmus  paper  turns  red,  lime  is  needed  and 
should  be  applied  as  above  directed.  If  neither  the  red  nor  the  blue 
litmus  paper  should  change  color,  then  the  reaction  of  the  soil  is 
neutral  and  small  applications  of  ground  limestone,  not  to  exceed 
one  ton  per  acre,  will  be  sufficient. 

WHEN   AND    HOW   GYPSUM    MAY    BE    USED 

Gypsum  may  be  used  with  advantage  on  alfalfa  fields  to  stimu- 
late growth.  This  is  especially  to  be  remembered  in  connection  with 
alfalfa  fields  of  several  years'  standing  in  which  bare  patches  are 
found.  An  application  of  gypsum  in  such  cases,  not  to  exceed  three 
hundred  or  four  hundred  pounds  to  the  acre,  along  with  fall-disking, 
will  usually  stimulate  the  plants  and  rejuvenate  the  field.  The  reason 
for  this  is  believed  to  be  that  gypsum  is  a  stimulant  to  the  alfalfa  plant 
itself  and  to  the  nitrogen-gathering  bacteria  that  grow  in  the  nodules 
on  its  roots. 

If  lime  is  very  expensive,  as  it  may  be  in  some  districts  of  this 
state,  gypsum,  if  much  cheaper,  may  also  be  used  as  indicated  above, 
to  lighten  heavy  soils.  Applications  varying  from  one-half  ton  to  one 
ton  per  acre  may  be  used  in  such  cases. 

Another,  but  more  limited,  use  for  gypsum  consists  in  applying  it 
to  ' '  black  alkali ' '  land  to  neutralize  or  make  harmless  the  black  alkali. 
In  this  respect  gypsum  cannot  be  replaced  by  lime.  The  quantities 
to  be  used  in  such  cases  depend  on  the  amount  of  black  alkali  present 
in  the  soil.  This  will  be  determined  for  those  interested,  by  the  Cali- 
fornia Agricultural  Experiment  Station,  upon  application.  Address 
College  of  Agriculture,  Berkeley,  California. 

NOTES   ON   LIMING 

1.  Lime  should  not  be  added  to  the  soil  at  the  same  time  as  organic 
matter.     Manure  or  cover  crops  should  first  be  turned  under  and 
about  a  month  later  lime  added  to  the  surface  and  harrowed  or 
disked  in. 

2.  The  fineness  of  ground  limestone  is  an  important  factor  in  its 
availability  and  use  in  the  soil.    If  ninety  per  cent  passes  through  a 


forty-  or  fifty-mesh  sieve  it  will  be  satisfactory  for  general  use,  at  \ 
least  for  soils  of  light  texture.  *^  j 

3.  Quicklime  and  hydrated  lime  are  usually  the  best  forms  to  add 
to  acid  soils.    These  more  active  agents  reduce  the  acidity  quickly  and 
soon  stimulate  plant  growth.     After  their  application  ground  lime- 
stone may  be  used. 

4.  The  beneficial -results  of  lime  are  most  marked  where  legumes 
are  grown  in  the  rotation  and  on  soils  well  supplied  with  organic 
matter. 

5.  Field  tests  with  annual  crops,  preferably  legumes,  as  indicators, 
are  the  most  reliable  criteria  for  determining  the  amount  and  form 
of  lime  needed  for  the  best  results  on  the  different  kinds  of  soil  and 
for  the  types  of  agriculture  practiced. 

6.  A  more  dependable  source  and  supply  of  the  different  forms  of 
lime  and  gypsum  at  a  less  cost  is  greatly  needed  for  the  welfare  of 
agriculture  in  most  of  California. 


